In general, the ability to detect cancer in a sensitive manner is critical to proper diagnosis and subsequent treatment. Although significant to all forms of cancer, sensitive detection of thyroid cancer is of particular importance. The incidence of thyroid cancer is increasing, with over 19,000 new cases in the United States per year. Thyroid nodules are extremely common in the general population. The discernment of which nodules require surgical excision is of paramount importance, as only 5% of nodules are malignant. In current clinical practice, this determination involves the isolation and use fine needle aspirates (FNA) followed by histological analysis. This test is sensitive and specific for the majority of thyroid cancers. However, when cytological specimens are graded “non-diagnostic” (10-15%) or as “follicular neoplasm” (5-10%), this usually results in surgical removal by hemithyroidectomy to determine carcinoma from benign growth.
Enzyme Linked Immunosorbent Assay (ELISA) is a biochemical technique used in biochemistry, clinical chemistry, and immunology to detect the presence of an antigen in a specific sample. In ELISA an unknown amount of antigen is affixed to a surface, and then a specific antibody is washed over the surface so that it can bind to the antigen. This antibody is linked to an enzyme, and in the final step a substance is added that the enzyme can convert to some detectable signal. Galectin-3, a protein that is present in elevated amounts in patients having thyroid malignancies and other cancers, has been detected using these kits in a variety of complex biologic samples including FNA. These kits typically use a rabbit derived antigalectin-3 linked to a horseradish peroxidase enzyme, and a biotin conjugated label molecule. The detection of Galectin-3 in biologic fluids using commercially available ELISA kits has yielded mixed results. Additionally, ELISA may not be applicable to other biological samples such as serum. Finally, ELISA cannot detect multiple protein or peptide biomarkers, which can provide more sensitive detection that ultimately results in better diagnosis of cancer.